Investigators are unsure what caused the fire, but say the way the building was built and what was inside caused the fire to spread more quickly.

"You have wide open space. You have the bowling lanes themselves that are obviously wood and are made of flammable material and combustible coverings that they are coated with," says Des Moines Fire Department spokesperson Brian O'Keefe.

Along with local investigators, federal agents are on scene due to the amount of damage and size of the property.